MCP1665T-E/MRA

MCP1665 High-Voltage 3.6A Integrated Switch PFM/PWM Boost Regulator Features • 36V, 100 m Integrated Switch • Up to 92% Efficiency • Higher Current Compared to the Previous MCP166x Switchers Family • Output Voltage Range: Up to 32V • 3.6A Typical Peak Input Current Limit: - IOUT > 1 A at 5.0V VIN, 12V VOUT - IOUT > 700 mA at 3.3V VIN, 12V VOUT - IOUT > 400 mA at 4.2V VIN, 24V VOUT • Input Voltage Range: 2.9V to 5V • Input Undervoltage Lockout (UVLO): - UVLO at VIN Rising: 2.9V, typical - UVLO at VIN Falling: 2.7V, typical • No Load Input Current: 250 µA Typically for Pulse-Frequency Modulation (PFM), 500 µA Typically for Pulse-Width Modulation (PWM) • Shutdown Mode with 0.4 µA Typical Quiescent Current • Automatically PFM/PWM or Selected by the MODE Pin, for High Efficiency • 500 kHz PWM Operation with Skipping Mode Operation Selectable by Dedicated MODE Pin • Feedback Voltage Reference: VFB = 1.2V • Cycle-by-Cycle Current Limiting • Internal Compensation • Inrush Current Limiting and Internal Soft Start • Output Overvoltage Protection (OVP) and OpenLoad Protection (OLP) for Constant Current Configuration • Thermal Shutdown • Easily Configurable for Single-ended Primaryinductor Converter (SEPIC), Cuk or Flyback Topologies • Available Package: 10-Lead 2x2 mm VQFN Applications • Three-Cell Alkaline, Lithium and NiMH/NiCd Portable Products • Single-Cell Li-Ion to 5V, 12V or 24V Converters • LCD Bias Supply for Portable Applications • Camera Phone Flash • Flashlight • Battery-Powered LEDs • Lighting Applications  2017 Microchip Technology Inc. • Portable Medical Equipment • Hand-Held Instruments General Description The MCP1665 device is a compact, high-efficiency, fixed-frequency, nonsynchronous step-up DC-DC converter that integrates a 36V, 100 m NMOS switch. It provides a space-efficient high-voltage step-up power supply solution for applications powered by either three-cell alkaline, Ultimate Lithium, NiCd, NiMH, one-cell Li-Ion or Li-Polymer batteries. The integrated switch is protected by the typical 3.6A cycle-by-cycle inductor peak current limit operation. There is an output overvoltage protection and an openload protection that turn off switching so that if the feedback resistors are accidentally disconnected, the feedback pin is short-circuited to GND or the output is exposed to excessive voltage. Soft Start circuit allows the regulator to start-up without high inrush current or output voltage overshoot from a low-voltage input. The device features an UVLO which avoids start-up and operation with low inputs or discharged batteries for cell-powered applications. A PFM switching mode (used for power saving) is implemented and it is selectable by the dedicated MODE pin. For standby applications (EN = GND), the device stops switching, enters Shutdown mode and consumes 0.4 µA of (typical) input current (feedback divider current not included). MCP1665 is easy to use and allows creating classic boost, SEPIC or flyback DC-DC converters within a small Printed Circuit Board (PCB) area. All compensation and protection circuitry are integrated to minimize the number of external components. Ceramic input and output capacitors are used. Package Types MCP1665 2 x 2 mm VQFN* PGND PGND 1 10 9 SW PGND 2 EP 0 8 SW SGND 3 FB 4 5 MODE 7 EN 6 VIN *Includes Exposed Thermal Pad (EP); see Table 3-1 DS20005872A-page 1 MCP1665 Typical Applications 3.6V-4.2V Ni-Cd SW RTOP 180 k VIN - + MCP1665 Ni-Cd PFM/PWM VFB MODE PWM Only - 12V 1 A U1 CIN 2x10 µF + VOUT D 20V 2A L 4.7 µH VIN EN + COUT 4x10 µF RBOT 20 k GND Ni-Cd ON OFF - D 40V 1A L 10 µH C 2x10 µF SW IN V IN VOUT 24V, >350 mA 3.3V-4.2V VIN TOP MCP1665 VFB MODE Li-Ion + RTOP 383 k C 15 pF COUT 4x10 µF RBOT 20 k EN GND - Best Efficiency vs. IOUT 100 VIN=5V VOUT=12V 90 Efficiency (%) 80 VIN=3.6V 70 60 50 40 30 20 10 PWM/PFM PWM ONLY 0 0.1 DS20005872A-page 2 1 10 IOUT (mA) 100 1000  2017 Microchip Technology Inc. MCP1665 1.0 ELECTRICAL CHARACTERISTICS Note: Stresses above those listed under “Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational sections of this specification is not intended. Exposure to maximum rating conditions for extended periods may affect the device’s reliability. Absolute Maximum Ratings EN, VIN,VFB – GND ........................................................+5.5V VSW – GND .....................................................................+36V Power Dissipation ....................................... Internally Limited Storage Temperature ................................... –65°C to +150°C Ambient Temperature with Power Applied ... –40°C to +125°C Operating Junction Temperature.................. –40°C to +150°C ESD Protection On All Pins: HBM ................................................................. 4 kV MM ..................................................................300V TABLE 1-1: DC AND AC CHARACTERISTICS Electrical Specifications: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH. Boldface specifications apply over the controlled TA range of –40°C to +125°C. Parameters Input Voltage Range Sym. Min. Typ. Max. Units Conditions VIN 2.7 — 5 V Note 1 UVLOSTART 2.7 2.85 3 V VIN rising, IOUT = 25 mA resistive load UVLOSTOP 2.5 2.65 2.8 V VIN falling, IOUT = 25 mA resistive load Output Voltage Adjust Range VOUT VIN +1V — 32 V Note 1 Maximum Output Current IOUT — 1000 — mA 5.0V VIN, 12V VOUT 10% drop (Note 4) — 700 — mA 3.3V VIN, 12V VOUT 10% drop (Note 4) — 400 — mA 4.2V VIN, 24V VOUT 10% drop (Note 4) 1.164 1.2 1.236 V Undervoltage Lockout (UVLO) Feedback Voltage VFB Accuracy VFB — — -3 — 3 % — Feedback Input Bias Current IVFB — 10 — nA — No Load Input Current (PFM) IIN0 — 250 — µA Device switching, no load, MODE = VIN (Note 2, Note 4) Shutdown Quiescent Current IQSHDN — 0.4 2.5 µA EN = GND, feedback divider current not included (Note 3) Peak Switch Current Limit ILmax — 3.6 — A Note 4 NMOS Switch Leakage INLK — 0.3 — µA VIN = VSW = 5V; VEN = VFB = GND RDS(ON) — 0.1 —  VGS = 3.6V, Peak Limit = 3.6A (Note 4) |(VFB/VFB)/ VIN| — 0.02 0.1 %/V NMOS Switch ON Resistance Line Regulation Note 1: 2: 3: 4: VIN = 3V to 5V, IOUT = 150 mA Minimum input voltage in the range of VIN (VIN ≤ 5V < VOUT) depends on the maximum duty cycle (DCMAX) and on the output voltage (VOUT), according to the boost converter equation: VINmin = VOUT x (1 – DCMAX). (VOUT – VIN) > 1V is required for boost applications. IIN0 varies with input and output voltage and input capacitor leakage (Figure 2-8). IIN0 is measured on the VIN pin when the device is switching (EN = VIN), at no load, with RTOP = 180 k and RBOT = 20 k. IQSHDN is measured on the VIN pin when the device is not switching (EN = GND), at no load, with the feedback resistors (RTOP + RBOT) disconnected from VOUT. Determined by characterization, not production tested.  2017 Microchip Technology Inc. DS20005872A-page 3 MCP1665 TABLE 1-1: DC AND AC CHARACTERISTICS (CONTINUED) Electrical Specifications: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH. Boldface specifications apply over the controlled TA range of –40°C to +125°C. Parameters Load Regulation Sym. Min. Typ. Max. Units Conditions |VFB/VFB| — 0.2 — % IOUT = 50 mA to 600 mA, PWM only operation (Note 4) Note 4 Maximum Duty Cycle DCMAX — 90 — % Switching Frequency fSW 425 500 575 kHz ±15% EN Input Logic High VIH 70 — — % of VIN IOUT = 1 mA EN Input Logic Low VIL — — 18 % of VIN IOUT = 1 mA EN Input Leakage Current IENLK — 5 — nA MODE Input Logic High — 54 — — % of VIN IOUT = 10 mA, Note 4 MODE Input Logic Low — — — 27 % of VIN IOUT = 10 mA, Note 4 MODE Input Leakage Current — — 5 — nA VMODE = 5V Soft-Start Time tSS — 3.7 — ms TA, EN Low-to-High, 90% of VOUT Thermal Shutdown Die Temperature TSD — 150 — °C Note 4 TSDHYS — 15 — °C Note 4 Die Temperature Hysteresis Note 1: 2: 3: 4: VEN = 5V Minimum input voltage in the range of VIN (VIN ≤ 5V < VOUT) depends on the maximum duty cycle (DCMAX) and on the output voltage (VOUT), according to the boost converter equation: VINmin = VOUT x (1 – DCMAX). (VOUT – VIN) > 1V is required for boost applications. IIN0 varies with input and output voltage and input capacitor leakage (Figure 2-8). IIN0 is measured on the VIN pin when the device is switching (EN = VIN), at no load, with RTOP = 180 k and RBOT = 20 k. IQSHDN is measured on the VIN pin when the device is not switching (EN = GND), at no load, with the feedback resistors (RTOP + RBOT) disconnected from VOUT. Determined by characterization, not production tested. TABLE 1-2: TEMPERATURE SPECIFICATIONS Electrical Specifications: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH and 10Lead 2x2 mm VQFN package. Boldface specifications apply over the controlled TA range of -40°C to +125°C. Parameters Sym. Min. Typ. Max. Units Conditions Operating Junction Temperature Range TJ –40 — +125 °C Storage Temperature Range TA –65 — +150 °C — Maximum Junction Temperature TJ — — +150 °C Transient JA — 48.3 — °C/W Temperature Ranges Steady State Package Thermal Resistances Thermal Resistance, 10LD-VQFN2x2 mm DS20005872A-page 4 —  2017 Microchip Technology Inc. MCP1665 2.0 TYPICAL PERFORMANCE CURVES Note: The graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. The performance characteristics listed herein are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified operating range (for example, outside specified power supply range) and therefore outside the warranted range. Note: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH and 10-Lead 2x2 mm VQFN package. 3 3 VOUT=6V L=4.7uH 2 UVLO START IOUT (A) Input Voltage (V) 2.5 2.9 2.8 VOUT=12V L=4.7uH 1.5 1 2.7 0.5 UVLO STOP 2.6 0 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (°C) FIGURE 2-1: Undervoltage Lockout (UVLO) vs. Ambient Temperature. 3 3.5 4 VIN (V) 4.5 5 FIGURE 2-3: Maximum Output Current vs. VIN (VOUT in Regulation with Maximum 10% Drop). 1.198 100 VOUT=6V 90 1.196 80 1.194 VIN=3V 1.192 VIN=3.6V VIN=5V 1.19 1.188 Efficiency (%) Feedback Voltage (V) VOUT=24V L=10uH 70 VIN=4.5V 60 VIN=3.6V 50 40 VIN=3V 30 20 1.186 10 1.184 -40 -25 -10 5 20 35 50 65 80 95 110 125 Temperature (°C) FIGURE 2-2: VFB Voltage vs. Ambient Temperature and VIN.  2017 Microchip Technology Inc. 0 0.001 PWM/PFM PWM ONLY 0.01 0.1 1 IOUT (A) FIGURE 2-4: IOUT. 6.0V VOUT Efficiency vs. DS20005872A-page 5 MCP1665 Note: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH and 10-Lead 2x2 mm VQFN package. 600 100 VOUT=12V No Load Input Current (µA) VOUT=12V Efficiency (%) 90 80 VIN=5V 70 VIN=4.5V 60 VIN=3.6V 50 VIN=3V 40 30 0.001 PWM/PFM PWM ONLY 0.01 0.1 PWM only 500 400 300 PFM/PWM 200 100 1 3 3.5 4 Input Voltage (V) IOUT (A) FIGURE 2-5: IOUT. 12.0V VOUT Efficiency vs. 0.8 IQ Shutdown Current (µA) VOUT=24V Efficiency (%) 80 VIN=5V 70 60 VIN=4.5V VIN=3.6V 50 VIN=3V 40 30 20 10 0 0.001 PWM/PFM PWM ONLY Note: Without FB Resistor Divider Current 0.7 0.6 0.5 0.4 VOUT=12V 0.3 VOUT=6V 0.2 VOUT=24V 0.1 0 0.01 0.1 3 1 3.25 3.5 IOUT (A) 24.0V VOUT Efficiency vs. FIGURE 2-6: IOUT. 3.75 4 4.25 VIN (V) 4.5 4.75 5 FIGURE 2-9: Shutdown Quiescent Current, IQSHDN vs. VIN (EN = GND). 500 4.3 VOUT=12V No Load Input Current (µA) Inductor Peak Current Limit (A) 5 FIGURE 2-8: No Load Input Current, IIN0 vs. VIN (EN = VIN). 100 90 4.5 VOUT=6V 4.1 VOUT=12V 3.9 VOUT=24V 375 PWM VIN=5V PFM VIN=3.6V 250 PWM VIN=3.6V PFM VIN=5V 125 0 -40 -25 -10 3.7 3 3.5 FIGURE 2-7: vs. Input Voltage. DS20005872A-page 6 4 VIN (V) 4.5 5 Inductor Peak Current Limit 5 20 35 50 65 80 95 110 125 Temperature (°C) FIGURE 2-10: No Load Input Current, IIN0 vs. Ambient Temperature.  2017 Microchip Technology Inc. MCP1665 Note: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH and 10-Lead 2x2 mm VQFN package. 100 VIN=3.6V VOUT=12V IOUT=200 mA 550 Enable Thresholds (% of VIN) Switching Frequency (kHz) 575 525 500 475 450 80 HIGH 70 60 50 40 30 LOW 20 10 0 425 -40 -15 10 35 60 Temperature (°C) FIGURE 2-11: Temperature. 85 3 110 3.5 FIGURE 2-14: Voltage. fSW vs. Ambient 4 Input Voltage (V) 4.5 5 Enable Threshold vs. Input 0.15 140 VOUT=6V PWM Only Switch RDSON (:) 120 100 IOUT (mA) VOUT=12V IOUT=1mA 90 80 60 0.1 0.05 VOUT=12V 40 20 VOUT=24V 0 3 0 3 3.25 3.5 3.75 4 4.25 Input Voltage (V) 4.5 4.75 FIGURE 2-12: PWM Pulse Skipping Mode Threshold vs. VIN. 140 PFM/PWM 3.5 5 FIGURE 2-15: vs. VIN. 4 Input Voltage (V) 4.5 5 N-Channel Switch RDSON VOUT 20 mV/div AC Coupled 20 MHz BW VOUT=6V 120 IOUT (mA) 100 VSW 5V/div 80 60 VOUT=12V 40 20 IL 200 mA/div VOUT=24V 0 3 3.25 FIGURE 2-13: 3.5 3.75 4 4.25 Input Voltage (V) 4.5 4.75 5 PFM/PWM Mode Threshold.  2017 Microchip Technology Inc. 20 µs/div IOUT = 5 mA FIGURE 2-16: 12.0V VOUT Light Load PWM Mode Waveforms. DS20005872A-page 7 MCP1665 Note: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH and 10-Lead 2x2 mm VQFN package. VOUT 100 mV/div AC Coupled 20 MHz BW VOUT 5V/div VSW 5V/div VIN 2V/div VSW 5V/div IL 500 mA/div 1 ms/div 400 µs/div IOUT = 5 mA FIGURE 2-17: 12.0V VOUT Light Load PFM Mode Waveforms. VOUT 50 mV/div AC Coupled 20 MHz BW FIGURE 2-20: (VIN = VENABLE). IOUT = 100 mA 12.0V Start-Up VOUT 100 mV/div AC Coupled 20 MHz BW VSW 5V/div IOUT 20 to 200 mA IOUT 100 mA/div IL 500 mA/div 2 µs/div FIGURE 2-18: Waveforms. 2 ms/div IOUT = 300 mA High-Load PWM Mode VIN = 3.6V FIGURE 2-21: 12.0V VOUT Load Transient Waveforms for PWM only (MODE = GND). VOUT 100 mV/div AC Coupled 20 MHz BW VOUT 5V/div VSW 5V/div IOUT 20 to 200 mA IL 500 mA/div IOUT 100 mA/div VEN 5V/div 1 ms/div FIGURE 2-19: DS20005872A-page 8 IOUT = 100 mA 12.0V Start-Up from Enable. 2 ms/div VIN = 3.6V FIGURE 2-22: 12.0V VOUT Load Transient Waveforms for PFM/PWM (MODE = VIN).  2017 Microchip Technology Inc. MCP1665 Note: Unless otherwise specified, all limits apply for typical values at ambient temperature TA = +25°C, VIN = 3.6V, IOUT = 25 mA, VOUT = 12V, CIN = 22 µF, COUT = 40 µF, X7R ceramic, L = 4.7 µH and 10-Lead 2x2 mm VQFN package. VOUT 50 mV/div AC Coupled 20 MHz BW VIN 3V to 5V VIN 1V/div 1 ms/div FIGURE 2-23: Waveforms. IOUT = 100 mA 12.0V VOUT Line Transient  2017 Microchip Technology Inc. DS20005872A-page 9 MCP1665 NOTES: DS20005872A-page 10  2017 Microchip Technology Inc. MCP1665 3.0 PIN DESCRIPTIONS The descriptions of the pins are listed in Table 3-1 . TABLE 3-1: PIN FUNCTION TABLE MCP1665 10Lead 2X2 mm VQFN 3.1 Symbol Description 1 PGND Power Ground Pin 2 PGND Power Ground Pin 3 SGND Signal Ground Pin 4 VFB 5 MODE 6 VIN Input Voltage Pin 7 EN Enable Control Input Pin EN = GND: device is in shutdown EN = VIN: device switching 8 SW Switch Node, Boost Inductor Input Pin 9 SW 10 PGND 0 EP Feedback Voltage Pin MODE select pin MODE = GND: device is switching in PWM only MODE = VIN: device is switching in PFM for light load Switch Node, Boost Inductor Input Pin Power Ground Pin Exposed Thermal Pad (EP); must be connected to Ground. Power Ground Pin (PGND) The power ground pin is used as a return for the high-current N-Channel switch. The signal ground and power ground must be connected externally in one point. 3.2 Signal Ground Pin (SGND) The signal ground pin is used as a return for the integrated reference voltage and error amplifier. The signal ground and power ground must be connected externally in one point. 3.3 Feedback Voltage Pin (VFB) The VFB pin is used to provide output voltage regulation by using a resistor divider. The VFB voltage is 1.2V typical. 3.4 MODE Select Pin 3.6 Enable Pin (EN) The EN pin is a logic-level input used to enable or disable device switching and to lower the quiescent current while disabled. A logic high will enable regulator’s output. A logic low will ensure that the regulator is disabled. 3.7 Switch Node Pin (SW) Connect the inductor from the input voltage to the SW pin. The SW pin carries inductor current, which is 3.6A peak (typical). The integrated N-Channel switch drain is internally connected to the SW node. 3.8 Exposed Thermal Pad (EP) There is no internal electrical connection between the Exposed Thermal Pad (EP) and the SGND and PGND pins. PGND, SGND and EP must be connected together in one low-impedance ground point. A separate ground plane is recommended. This pin selects the power saving mode between PFM/ PWM (MODE = VIN) and PWM only (MODE = GND). 3.5 Power Supply Input Voltage Pin (VIN) Connect the input voltage source to VIN. The input source must be decoupled with a 22 µF (minimum) capacitor to GND.  2017 Microchip Technology Inc. DS20005872A-page 11 MCP1665 NOTES: DS20005872A-page 12  2017 Microchip Technology Inc. MCP1665 4.0 DETAILED DESCRIPTION 4.1 Device Overview MCP1665 is a constant frequency PFM/PWM boost (step-up) converter, based on a peak current mode control architecture, which delivers high efficiency over a wide load range, from three-cell Alkaline, Ultimate Lithium, NiMH, NiCd and single-cell Li-Ion battery inputs. A high level of integration lowers the total system cost, eases implementation and reduces board area. The device features controlled start-up voltage (UVLO), adjustable output voltage, 500 kHz switching frequency, PFM/PWM mode or PWM/skipping selectable by the dedicated MODE pin, 36V integrated switch, internal compensation, inrush current limit, soft start and overvoltage/open load protections (in case the VFB connection is lost). The typical 100 m, 36V integrated switch is protected by the 3.6A (typical) cycle-by-cycle peak inductor current limit. When the ENABLE pin is pulled to ground (EN = GND), the device stops switching, enters in Shutdown mode and consumes approximately 0.4 uA of input current (feedback current is not included). MCP1665 can be used to design classic boost, SEPIC or flyback DC-DC converters.  2017 Microchip Technology Inc. DS20005872A-page 13 MCP1665 4.2 Functional Description The MCP1665 device is a compact, high-efficiency, fixed-frequency, step-up DC-DC converter, that provides an easy-to-use high-output power supply solution for applications powered by either three-cell Alkaline or Lithium Energizer, three-cell NiCd or NiMH, one-cell Li-Ion or Li-Polymer, or two-cell lead-acid batteries. FIGURE 4-1: 4.2.1 MCP1665 Simplified Block Diagram. INTERNAL BIAS The MCP1665 device gets its bias from the VIN pin. The VIN bias is used to power the device and drive circuits over the entire operating range. The maximum VIN is 5V. If a higher input voltage is required, the VIN pin should be separately powered within its specified voltage range. An example is available in Figure 6-3. Other examples can be found in AN2085 “Designing Applications with MCP166X High Output Voltage Boost Converter Family.” DS20005872A-page 14 Figure 4-1 depicts the functional block diagram of the MCP1665 device. It incorporates a current-mode control scheme, in which the PWM ramp signal is derived from the NMOS power switch current (VSENSE). This ramp signal adds slope ramp compensation signal (VRAMP) and is compared to the output of the error amplifier (VERROR) to control the on-time of the power switch. 4.2.2 START-UP VOLTAGE AND SOFT START The MCP1665 device starts at input voltages that are higher than or equal to a predefined set UVLO value. MCP1665 starts switching at 2.85V (typical) for a 12V output (25 mA load). Once started, the device will continue to operate under normal load conditions, down to 2.7V (typical). A soft-start feature is present and it provides a way to limit the inrush current drawn from the input (batteries) during start-up. The soft start  2017 Microchip Technology Inc. MCP1665 has an important role in applications where the switch voltage will reach 32V. During start-up, excessively high switch current, together with the presence of high voltage, can overstress the NMOS switch. When the device is powered (EN = VIN and VIN rises from zero to its nominal value), the output capacitor charges to a value close to the input voltage (or VIN minus a Schottky diode voltage drop). The overshoot on output is limited by slowly increasing the reference of the error amplifier. There is an internal reference voltage circuit that charges an internal capacitor with a weak current source. The voltage on this capacitor slowly ramps the reference voltage. The soft-start capacitor is completely discharged in the event of a commanded shutdown or a thermal shutdown. Due to the direct path from input to output, in the case of start-up by enable (EN voltage switches from low-tohigh), the output capacitor is already charged and the output starts from a value close to the input voltage (Figure 2-19). The internal oscillator has a delayed start in order to let the output capacitor completely charge to the input voltage value. 4.2.3 UNDERVOLTAGE LOCKOUT (UVLO) MCP1665 features an UVLO that prevents fault operation below 2.7V, which corresponds to the value of three discharged primary cells. The device starts its normal operation at 2.85V (typical) input. The upper limit is set to avoid any input transients (temporary VIN drop), which might trigger the UVLOSTOP threshold and restart the device. Usually, these voltage transients (overshoots and undershoots) have up to a few hundreds mV. MCP1665 is a nonsynchronous boost regulator. Due to this fact, there is a direct path from VIN to VOUT through the inductor and the diode. This means that, while the device is not switching (VIN below UVLOSTOP threshold, when EN = GND and during thermal shutdown), VOUT is not zero, but equal to VIN – VF, (where VF is the voltage drop on the rectifying diode). See Section 2.0 “Typical Performance Curves” for more information. 4.2.4 PWM AND PFM MODE OPERATION MCP1665 operates as a fixed-frequency, nonsynchronous converter. The switching frequency is maintained at 500 kHz with a precision oscillator. Lossless current sensing converts the peak current signal to a voltage (VSENSE) and adds it to the internal slope compensation (VRAMP). This summed signal is compared to the voltage error amplifier output (VERROR) to provide a peak current control signal (VPWM) for the PWM control block. The slope compensation signal depends on the input voltage. Therefore, the converter  2017 Microchip Technology Inc. provides the proper amount of slope compensation to ensure stability. The inductor peak current limit is set to 3.6A typical. 4.2.5 1. MODE PIN FUNCTIONALITY MODE = GND The MCP1665 device will operate in PWM mode, even during light-load operation, by skipping pulses to keep the output regulation. By operating in PWM mode, the output ripple is low and the frequency is constant. 2. MODE = VIN The MCP1665 device will operate in PFM mode at light-load currents, resulting in a low-quiescent current consumption. During the sleep period between two consecutive bursts of switching cycles, MCP1665 consumes less than 30 µA (typical) from the supply, for its internal circuitry. The switching pulse bursts represent a small percentage of the total running cycle, so the overall average current drawn from the battery is reduced. The PFM mode shows higher output ripple voltage than the PWM mode and variable PFM mode frequency. The PFM to PWM mode threshold is a function of the input voltage, output voltage and load current. Note: 4.2.6 If a high-load current is required during the sleep time between two switching bursts of PFM (MODE = VIN), the output voltage drops more, compared to the PWM only (MODE = GND), before the output recovers. The reason is that during sleep mode, most of the internal circuitry of the switcher is turned off, in order to save input power. When steep load changes are expected and the output voltage ripple has to be always low, it is recommended to use the switcher in PWM only MODE = GND. ADJUSTABLE OUTPUT VOLTAGE The MCP1665 output voltage is adjustable with a resistor divider network from VIN + 1V to 32V. High value resistors are recommended to minimize power loss and keep the efficiency high at light loads. The device integrates a transconductance type error amplifier and the values of the feedback resistors do not influence the stability of the system. 4.2.7 MINIMUM INPUT VOLTAGE FOR A SPECIFIED OUTPUT CURRENT The maximum output current for which the device can regulate the output voltage depends on the input and the output voltage. The minimum input voltage necessary to reach the value of the desired voltage output depends on the maximum duty cycle, in accordance with the mathematical relationship VOUT = VINmin/(1 – DMAX). DS20005872A-page 15 MCP1665 As there is a typical 3.6A inductor peak current limit, VOUT can go out of regulation before reaching the maximum duty cycle. reference. Using an undervoltage feedback comparator, in addition to an UVLO input circuit, it acts as a permanently Low Battery device turning off. For example, to ensure a 800 mA load current for VOUT = 12.0V, a minimum of 3.6V input voltage is necessary. If an application is powered by one Li-Ion battery (VIN from 3.3V to 4.2V), the minimum load current the MCP1665 device can deliver is close to 350 mA at 24.0V output (see Figure 2-3). The OLP comparator is disabled during the start-up sequence and during a thermal shutdown event. 4.2.8 ENABLE PIN The MCP1665 device is enabled when the EN pin is set high. The device is set into Shutdown mode when the EN pin is set low. To enable the boost converter, the EN voltage level must be greater than 70% of the VIN voltage. To disable the boost converter, the EN voltage must be less than 18% of the VIN voltage. 4.2.11 OVERVOLTAGE PROTECTION (OVP) A dedicated comparator monitors VFB and if the voltage increases by 5% (typical) above the nominal value, the part stops switching until the voltage on the feedback pin drops to the nominal value. When proper feedback voltage is detected, the switching resumes. This is meant to protect the device against excessive output voltage or high overshoots during load steps. 4.2.12 INPUT OVER-CURRENT LIMIT In Shutdown mode, the MCP1665 device stops switching and all internal control circuitry is switched off. MCP1665's internal circuitry will consume in this state 0.4 µA (typical). In boost configuration, the input voltage will be bypassed to output through the inductor and the Schottky diode. The MCP1665 device uses a 3.6A (typical) cycle-by-cycle inductor peak current limit to protect the N-channel switch. There is an over-current comparator which resets the driving latch when the peak of the inductor current reaches the limit. In current limitation, the output voltage starts dropping. 4.2.9 4.2.13 INTERNAL COMPENSATION The error amplifier, with its associated compensation network, completes the closed-loop system by comparing a fraction of the output voltage to a reference at the input of the error amplifier and by feeding the amplified and inverted error voltage to the control input of the inner current loop. The compensation network provides phase leads and lags at appropriate frequencies to cancel excessive phase lags and leads of the power circuit. All necessary compensation components and slope compensation are integrated. 4.2.10 OPEN LOAD PROTECTION (OLP) An internal VFB fault signal turns off the PWM signal (VEXT) and MCP1665 stops switching in the event of: • short circuit of the feedback pin to GND • disconnection of the feedback divider from VOUT For a regular boost converter without any protection implemented, if the VFB voltage drops to ground potential, its N-Channel transistor is forced to switch at full duty cycle. As a result, VOUT rises and the SW pin’s voltage exceeds the maximum rating and damages the boost regulator IC, the external components and the load. Because a lower feedback voltage can cause an output voltage overshoot, a feedback undervoltage comparator can be used to protect the circuit. OUTPUT SHORT CIRCUIT CONDITION Like all nonsynchronous boost converters, MCP1665’s inductor current will increase excessively during a short-circuit at the converter’s output. Short circuit at the output will cause the rectifying diode to fail and the inductor’s temperature to rise. When the diode fails, the SW pin becomes a high-impedance node, it remains connected only to the inductor and the excessive resulted ringing will damage the MCP1665 device. 4.2.14 OVERTEMPERATURE PROTECTION Overtemperature protection circuitry is integrated into the MCP1665 device. This circuitry monitors the device’s junction temperature and shuts down the device if the junction temperature exceeds the typical 150°C threshold. If this threshold is exceeded, the device will automatically restart when the junction temperature drops by approximately 15°C. The output open load protection (OLP) is reset during an overtemperature condition to allow the resuming of the operation. The MCP1665 has implemented a protection which turns off PWM switching when the VFB pin’s voltage drops to ground level. An additional comparator uses a 80 mV (approximate) reference, monitors the VFB voltage and generates an internal VFB_FAULT signal for control logic circuits, if the voltage decreases under this DS20005872A-page 16  2017 Microchip Technology Inc. MCP1665 5.0 APPLICATION INFORMATION 5.1 Typical Applications The MCP1665 nonsynchronous boost regulator operates over a wide output voltage range, up to 32V. The input voltage ranges from 2.9V to 5V. The device operates down to 2.7V input, with limited specification. The UVLO thresholds are set to 2.85V, when VIN is ramping and to 2.7V, when VIN is falling. The power efficiency conversion is high for several decades of load range. Output current capability increases with the input voltage and decreases with the increasing output voltage. The maximum output current is based on an N-channel switch peak current limit set to 3.6A, and on a maximum duty cycle of 90%. Typical characterization curves in this data sheet are presented to display the typical output current capability. 5.2 Adjustable Output Voltage Calculations To calculate the resistor divider values for the MCP1665, Equation 5-1 can be used, where RTOP is connected to VOUT, RBOT is connected to GND and both are connected to the VFB input pin. EQUATION 5-1: R TOP V OUT  = R BOT   ------------–1  V  FB EXAMPLE 5-1: VOUT = 12.0V VFB = 1.2V RBOT = 20 k RTOP = 180 k EXAMPLE 5-2: VOUT = 24.0V VFB = 1.2V RBOT = 20 k RTOP = 380 k (VOUT = 24.18V with a standard value of 383 k) There are some potential issues with higher value resistors, as in the case of small surface mount resistors: environment contamination can create leakage paths on the PCB that significantly change the divider ratio, so it may affect the output voltage tolerance. 5.2.1 OPEN LOAD PROTECTION The MCP1665 device features an output open-load protection (OLP) in case RTOP is disconnected from the VOUT line. An 80 mV (approximate) OVP reference is compared to the VFB voltage. If the voltage on the VFB pin drops below the reference value, the device stops switching and prevents VOUT from rising up to a dangerous value. OLP is not enabled during start-up and thermal shutdown events. 5.3 Input Capacitor Selection The boost input current is smoothened by the boost inductor, reducing the amount of filtering necessary at the input. Some capacitance is recommended to provide decoupling from the input source. Due to the fact that MCP1665 is rated to work up to +125°C ambient temperature, low ESR X7R ceramic capacitors are well suited, since they have a low temperature coefficient and are small-sized. For limited temperature range use, at up to +85°C, an X5R ceramic capacitor can be used. For light-load applications, 22 µF of capacitance is sufficient at the input. Please note that if MCP1665’s power supply impedance cannot be kept as low as needed in order to maintain the input voltage permanently above the UVLO threshold, it is recommended to connect an electrolyte or a tantalum capacitor in parallel with the ceramic mentioned above. Otherwise, unwanted behaviors ( such as restarts, oscillation or bus-pumping) may be noticed while under high load. For high-power applications that have high source impedance or long leads (wires), using a 220-470 µF input capacitor, is recommended to sustain the high input boost currents. Additional input capacitance can also be added, to provide a stable input voltage during high load step-ups. Table 5-1 contains the recommended range for the input capacitor value. The values of the two resistors, RTOP and RBOT, affect the no load input current and quiescent current. In Shutdown mode (EN = GND), the device consumes 0.4 μA (typical). With 400 K feedback divider for 24V output, the current that the divider drains from the input is 9 μA. This value is higher than the current consumption of the device itself. Keeping RTOP and RBOT high will optimize efficiency conversion at very light loads.  2017 Microchip Technology Inc. DS20005872A-page 17 MCP1665 5.4 Output Capacitor Selection The output capacitor helps provide a stable output voltage during sudden load transients and reduces the output voltage ripple. As with the input capacitor, an X7R ceramic capacitor is recommended for this application. Using other capacitor types (aluminum or tantalum) with large ESR has an effect on the converter's efficiency, maximum output power and stability. For limited temperature range (up to 85°C), X5R ceramic capacitors can be used. The DC rating of the output capacitor should be greater than the VOUT value. Generally, ceramic capacitors lose much of their capacity when the voltage applied is close to their maximum DC rating. Choosing a capacitor with a safe higher DC rating or placing more capacitors in parallel assure enough capacity to correctly filter the output voltage. The MCP1665 device is internally compensated, so output capacitance range is limited. See Table 5-1 for the recommended output capacitor range. An output capacitance higher than 40 µF adds a better load step response and high-frequency noise attenuation, especially while stepping from light to heavy load currents. While the N-Channel switch is on, the output current is supplied by the output capacitor COUT. The amount of output capacitance and equivalent series resistance will have a significant effect on the output TABLE 5-2: voltage ripple. While COUT provides load current, a voltage drop also appears across its internal ESR that results in voltage ripple. A trade-off between load step behavior and loop's dynamic response speed should be done before increasing the COUT very much. Peak-to-peak output ripple voltage also depends on the equivalent series inductance (ESL) of the output capacitor. There are ceramic capacitors with special internal architecture that minimize the ESL. For output voltages that require low-ripple for high-frequency components, capacitors with low ESL (for instance, reverse geometries) are recommended. Consult the ceramic capacitor's manufacturer portfolio for more information. TABLE 5-1: CAPACITOR VALUE RANGE CIN COUT Minimum 22 µF 40 µF Maximum — 80 µF 5.5 Inductor Selection The MCP1665 device is designed to be used with small surface mount inductors; the inductance value can range from 4.7 µH to 10 µH. An inductance value of 4.7 µH is recommended for output voltages below 15V. For higher output voltages, up to 32V, an inductance value of 10 µH is optimum. MCP1665 RECOMMENDED INDUCTORS FOR BOOST CONVERTERS Part Number Value (µH) DCR (typ.) ISAT (A) Size WxLxH (mm) MSS1048-472 4.7 11.4 4.36 10.2x10x4.8 MSS1038-103 10 35 3.9 10.2x10x3.8 XAL5030-472ME 4.7 36 6.7 5.28x5.48x3.1 Coilcraft Wurth Elektronik 744778004 4.7 42 4.2 7.3x7.3x3.2 7447714047 4.7 10.4 8 10x10x5 7443340470 4.7 12.7 8 8.4x7.9x7.2 7447714100 10 23 5 10x10x5 74437368100 10 27 5.2 10x10x3.8 Bourns®, Inc. RLB0913-4r7k 4.7 20 4.3 8.5x12.5 Bourns, Inc. SRN6045-4R7Y 4.7 37.6 4 6x4.5 Panasonic® - ECG ELL8TP4R7NB 4.7 14 4 8x8x4.7 Various Several parameters are used to select the appropriate inductor: maximum-rated current, saturation current and copper resistance (DCR). For boost converters, the inductor current is much higher than the output current. The average inductor current is equal to the DS20005872A-page 18 input current. The inductor’s peak current is 30-40% higher than the average. The lower the inductor DCR is, the higher the efficiency of the converter: a common trade-off is size versus efficiency.  2017 Microchip Technology Inc. MCP1665 The saturation current typically specifies a point at which the inductance has rolled off a percentage of the rated value. This can range from a 20% to 40% reduction in inductance. As inductance rolls off, the inductor ripple current increases, as does the peak switch current. It is important to keep the inductance from rolling off too much, causing switch current to reach the peak limit and affecting output voltage regulation. 5.6 Rectifying Diode Selection Schottky diodes are used to reduce losses. The diode’s average forward current rating must be equal or higher than the maximum output current. The diode’s peak repetitive forward current rating has to be equal or higher than the inductor peak current. The diode’s reverse breakdown voltage must be higher than the internal switch rating voltage of 36V. The converter’s efficiency will be improved if the voltage drop across the diode is lower. The average forward voltage rating is forward-current dependent, which is equal in particular to the load current. At high temperature operation the diode’s leakage current can also have a significant effect on the converter’s operational efficiency. For high currents and high ambient temperatures, use a diode with good thermal characteristics. See Table 5-3 for recommended diodes. TABLE 5-3: RECOMMENDED SCHOTTKY DIODES VOUTmax Max TA STPS2L40 Type 32V